A weighted least-squares algorithm is examined for continuous-time linear deterministic systems. The convergence of the algorithm is discussed from several viewpoints. The necessity of the persistently exciting condition is stressed for the exponential convergence of the algorithm. The need and the effect of introducing the normalizing factor into the algorithm are also considered in relation to the global stability of the adaptive feedback control. Adaptive pole placement control by means of an adaptive observer is considered as a typical example of the application of the algorithm.